1. Field of the Invention
The present invention is directed to apparatus for use in preparing tissue sections for use in diagnostic histopathology and, more particularly, to an apparatus that automatically changes the blades of a microtome without exposure of the user to the cutting edges of the blades.
2. Description of Related Art
Microtomes have been used for many years to meet the exacting requirements necessary for thin sectioning of paraffin-embedded tissue. Essentially, microtomes are holders for razor-sharp metal blades, against which a block of paraffin-embedded tissue is moved in an up-and-down motion. Concurrently, either the tissue block is advanced against the blade, or vice versa, so that with each up or down stroke, a thin slice or “section” of tissue is cut from the block. The blades are highly engineered for the precise requirements of tissue sectioning. Specifically, the blades are capable of cutting sections as thin as 1 μm.
The present practice for tissue sectioning requires the blades be changed as they become dulled. This necessitates alleviating the pressure that the blade holder puts on the blade to keep it in place, usually be removing a clamping mechanism. Once the clamp is removed, the blade can be lifted off of the rest. Usually, this is accomplished by grasping the blade at an edge and discarding it in a sharps container, all of which is done by hand. This exposed the user to the edges of the blade, and of course the potential of serious injury. Additional exposure to the sharp blade occurs when loading a new blade and re-clamping it in position.
U.S. Pat. No. 3,667,330 (Kobernick) discloses an automated microtome assembly which includes a continuous flexible steel blade whose ends are mounted upon feed and takeup reels for intermittent motor-driven advancement to enable advancement of new cutting surface without contact by a user. The changing of the knife edge may be actuated manually or automatically. The '330 patent does not disclose a method or apparatus for the changing of individual blades, or provide safety features for the changing of the blade.
U.S. Pat. No. 4,207,790 (Endo) is directed to a knife holder and blade cassette for microtomes. The knife holder comprises a base plate and a holder plate for holding the knife edge onto the base plate. The blade cartridge is spring-loaded for biasing the blades upwardly towards the exit from the cartridge. To replace a blade, the user must first loosen the bolts holding the knife holder plate down, then engage the cartridge with the edge of the knife holder assembly, and finally slide a new blade out of the cartridge and into contact with the dull blade, thereby positioning a new blade beneath the holder plate and simultaneously pushing the dull blade out of position. There is no disclosure related to automation of the process, what happens to the spent blade, or safety features.
Blade changers for hand-held shavers are known. U.S. Pat. No. 1,817,512 (Gaisman) and U.S. Pat. No. 2,741,837 (Breazeale) disclose a cartridge containing individual blades wherein the blade is manually dispensed from the cartridge using an ejector, and at the end of the ejector stroke the blade is located in the cutting position, and the used blade is received in a take-up cartridge (see Gaisman, FIG. 11). U.S. Pat. No. 2,653,379 (Austin) discloses a box with a cartridge on either side of a razor. A slider pushes a new blade from the first cartridge onto the razor, which pushes the used blade into the second cartridge. U.S. Pat. No. 2,679,685 (Austin) discloses a razor blade changer where advancing a pusher causes a blade in supply cartridge C to advance into the razor and push the used blade out into take-up cartridge D. When cartridge C is empty, it is put in place of discarded cartridge D to act as the new take-up cartridge, and a full supply cartridge is put in place of cartridge C.
Patents on razor blade containers include U.S. Pat. No. 2,592,138 (Gwoosh et al.) for a razor blade package which teaches the use of a coil spring to bias blades towards the dispenser opening of a blade container. The top has a thumb opening to allow manual advance of the blades. U.S. Pat. No. 2,604,979 Roberts) shows a spring-loaded blade container which uses a leaf-spring U.S. Pat. No. 2,775,366 (Willhelm) discloses the use of a compression spring to urge a plurality of blades towards the package opening. U.S. Pat. No. 5,409,133 (Gringer) is a spring-loaded blade dispenser wherein the entire top except guide rails, is open for application of a manual dispensing force. The dispenser is also capable of receiving spent blades back through a disposal opening 34 (see FIGS. 9–10). None of the above mentioned patents are adapted for automatic use.
There is a need for an automated microtome blade changing system that safeguards the user against being seriously injured, and enhances the work flow in the pathology laboratory.